Frederick Hess is director of educational-policy studies at the American Enterprise Institute.

New Jersey last week approved a record number of charter schools, wading deeper into the national debate over whether these alternative public schools actually work. So far, charters have had mixed results. They haven’t been shown to be consistently better than traditional district schools, says Frederick Hess, a recognized expert on the subject. Hess is the director of education policy studies at the American Enterprise Institute, and also serves on the board of directors of the National Association of Charter School Authorizers and authored a recent article in National Affairs, “Does School Choice ‘Work’?” Recently, he spoke with editorial writer Julie O’Connor about the school choice movement today.

Q. You’ve studied all the data on school choice. Where is it most promising? Or least promising?

A. School choice is most promising in places like Newark, where you have families with real concerns about the schools. They don’t have the means to move somewhere with better schools or afford private school tuition. It’s least promising in sparsely populated communities, where it’s difficult to establish enough schools to make for viable choices.

Q. Is there good evidence that competition from charters improves traditional schools?

A. When we talk about competition, what we usually mean is: Does it force a competitor to go back, re-examine the business model and seek out dramatic opportunities to do better or become more cost-efficient? I think we’ve seen little evidence that competition has thus far pressed traditional schools to do that. We’ve created funding mechanisms and written rules that insulate traditional district schools from the impact of competition and encourage them to focus on politics and lobbying rather than improving their performance.

Q. Some successful school districts in New Jersey say siphoned-off money hurts their programs by draining resources. What’s your reaction?

A. That presumes the dollars are the school district’s, which makes sense if you’re a school district official. Another way to think about this is that the citizens of New Jersey are spending these dollars to educate each child. If a family chooses an alternative educational environment that the state recognizes as legitimate, I wonder why that district should have claim to any of the dollars being spent on that kid’s behalf. Those dollars should flow to the school that will educate that child.

Q. The New Jersey Charter Schools Association says charters get on average about 70 percent of what district schools get and, in addition, have no capital. Is that typical and is it fair?

A. That’s ballpark. I’m less inclined to talk about it as fair. When we look at comparative performance, we ought to be looking at bang for the buck. If charters are spending 70 percent of what a district school is spending — and even less when we add in the facilities dollars a district receives — then the fact that a charter school’s kids are making similar or better progress tells a different story.

Q. New Jersey is considering diverting public school money into private school vouchers. What’s the record on that?

A. In Boston and New York, where you have vibrant charter sectors with strong leadership and self-policing, it’s pretty clear kids are seeing real benefits. When you look at performance nationally, it’s not clear kids in charters do any better. It depends on the quality of the schools participating in the choice program. In a place like Newark, given just how challenged some of the district schools appear to be, it’s pretty obvious children would stand to benefit.

Q. If you have choice through charter schools, do you need vouchers as well?

A. I think so. Charter schools by definition are not permitted to have a religious mission. If you want to have that as an option for low-income families who can’t afford to pay tuition to a private religious school, a voucher program makes sense. Families with a certain amount of income are always able to access a school with an overtly religious mission.

Q. Lots of charter schools fail. What should be done then?

A. First, we ought to keep in mind that some traditional district schools have been failing by the same metrics for decades. What we need to do with lousy charters is make sure they go out of business. One of the important challenges in recent years has been cleaning up some of the lousy schools that put down roots since the early 1990s. We should also be proactive about seeking out promising charter candidates. You want to stack the odds for them to succeed, which then makes it a lot easier to go after the weak performers and shut them down clean and quick.